Fair Value - Significant Unobservable Inputs Used for Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional default rate	4.02%
Minimum [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional default rate	0.50%	0.50%
Minimum [Member] | Mandatory Repurchase Obligation [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate
Loss severity
Minimum [Member] | Professional Fees Liability Related to Certain Securitizations [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		3.91%
Minimum [Member] | Mortgage-Backed Debt Related to Non-Residual Trusts [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		3.91%
Loss severity		72.70%
Minimum [Member] | HMBS Related Obligations [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Weighted-average remaining life in years		2 years 1 month
Conditional repayment rate		10.40%
Discount rate		0.92%
Minimum [Member] | Interest Rate Lock Commitments [Member] | Derivative Financial Instruments, Assets [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Loan funding probability		33.40%
Minimum [Member] | Interest Rate Lock Commitments [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Loan funding probability		19.20%
Minimum [Member] | Reverse Mortgage Loans [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Weighted-average remaining life in years		1 year 3 months
Conditional repayment rate		4.80%
Discount rate		1.39%
Minimum [Member] | Residential Loans Related to Non-Residual Trusts [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		3.82%
Loss severity		75.46%
Minimum [Member] | Receivables Related to Non-Residual Trusts [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		3.91%
Loss severity		72.70%
Minimum [Member] | Servicing Rights Carried at Fair Value [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Weighted-average remaining life in years		5 years
Discount rate		9.17%
Conditional prepayment rate		4.95%
Conditional default rate		0.92%
Maximum [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional default rate	2.00%	2.00%
Maximum [Member] | Mandatory Repurchase Obligation [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		6.92%
Loss severity		70.55%
Maximum [Member] | Professional Fees Liability Related to Certain Securitizations [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		6.83%
Maximum [Member] | Mortgage-Backed Debt Related to Non-Residual Trusts [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		6.22%
Loss severity		89.19%
Maximum [Member] | HMBS Related Obligations [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Weighted-average remaining life in years		7 years 5 months
Conditional repayment rate		36.00%
Discount rate		2.81%
Maximum [Member] | Interest Rate Lock Commitments [Member] | Derivative Financial Instruments, Assets [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Loan funding probability		100.00%
Maximum [Member] | Interest Rate Lock Commitments [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Loan funding probability		100.00%
Maximum [Member] | Reverse Mortgage Loans [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Weighted-average remaining life in years		11 years 6 months
Conditional repayment rate		36.10%
Discount rate		4.27%
Maximum [Member] | Residential Loans Related to Non-Residual Trusts [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		6.21%
Loss severity		91.76%
Maximum [Member] | Receivables Related to Non-Residual Trusts [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		6.22%
Loss severity		89.19%
Maximum [Member] | Servicing Rights Carried at Fair Value [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Weighted-average remaining life in years		9 years 3 months 18 days
Discount rate		10.40%
Conditional prepayment rate		10.37%
Conditional default rate		4.86%
Weighted Average [Member] | Mandatory Repurchase Obligation [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		6.92%
Loss severity		70.55%
Weighted Average [Member] | Professional Fees Liability Related to Certain Securitizations [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		5.55%
Weighted Average [Member] | Mortgage-Backed Debt Related to Non-Residual Trusts [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		5.49%
Loss severity		84.33%
Weighted Average [Member] | HMBS Related Obligations [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Weighted-average remaining life in years		4 years 2 months
Conditional repayment rate		19.47%
Discount rate		1.72%
Weighted Average [Member] | Interest Rate Lock Commitments [Member] | Derivative Financial Instruments, Assets [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Loan funding probability		80.00%
Weighted Average [Member] | Interest Rate Lock Commitments [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Loan funding probability		84.30%
Weighted Average [Member] | Reverse Mortgage Loans [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Weighted-average remaining life in years		4 years 5 months
Conditional repayment rate		18.46%
Discount rate		2.35%
Weighted Average [Member] | Residential Loans Related to Non-Residual Trusts [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		5.50%
Loss severity		87.00%
Weighted Average [Member] | Receivables Related to Non-Residual Trusts [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Conditional prepayment rate		5.49%
Loss severity		84.33%
Weighted Average [Member] | Servicing Rights Carried at Fair Value [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Weighted-average remaining life in years		5 years 4 months 24 days
Discount rate		9.37%
Conditional prepayment rate		9.31%
Conditional default rate		4.02%